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United States Patent |
6,033,453
|
Weddell, III
|
March 7, 2000
|
Re-usable frame support rack for replaceable pleated-media filter core
Abstract
A re-usable frame support rack is provided for supporting and retaining an
outstretched, replaceable pleated-media filter core. The pleated-media
filter core is of a type that has fold lines extending in a transverse
direction and that stretches-out/collapses in the longitudinal direction.
The support rack has a frame formed of spaced longitudinal rails extending
between spaced transverse rails. The frame carries a pressure-differential
support system that provides support, in instances when a pressure
differential exists across the frame, to the filter core on a low pressure
side thereof. The transverse rails preferably include fingers or like
gripping formations for releasably gripping the longitudinal margins of
the installed filter core. The longitudinal rails include gates or flaps
which have closed and open positions for allowing retention and
unobstructed removal in the closed and open positions, respectively, of
the longitudinal margins of the installed filter core. Given the foregoing
arrangement, the re-usable frame support rack provides convenient removal
and replacement of a spent filter core with little fuss.
Inventors:
|
Weddell, III; Robert W. (2320 E. Edgewood, Springfield, MO 65804)
|
Appl. No.:
|
015842 |
Filed:
|
January 29, 1998 |
Current U.S. Class: |
55/493; 55/497; 55/506; 55/DIG.31 |
Intern'l Class: |
B01D 027/06 |
Field of Search: |
55/497,493,506,DIG. 31
|
References Cited
U.S. Patent Documents
5273564 | Dec., 1993 | Hill | 55/497.
|
5501794 | Mar., 1996 | Van De Graaf et al. | 55/497.
|
5509950 | Apr., 1996 | Van De Graaf et al. | 55/497.
|
5531892 | Jul., 1996 | Duffy | 55/497.
|
5679122 | Oct., 1997 | Moll et al. | 55/497.
|
5792229 | Aug., 1998 | Sassa et al. | 55/497.
|
Primary Examiner: Simmons; David A.
Assistant Examiner: Pham; Minh-Chau T.
Attorney, Agent or Firm: Bay; Jonathan A.
Parent Case Text
CROSS-REFERENCE TO PROVISIONAL APPLICATION(S)
This application claims the benefit of U.S. Provisional Application No.
60/036,616, filed Jan. 30, 1997.
Claims
I claim:
1. A support rack for loading and unloading with replaceable, pleated-media
filter cores that have fold lines extending in a transverse direction and
which stretch-out/collapse in a longitudinal direction, the loaded support
rack allowing installation in a filter station of air-handling equipment,
the support rack comprising:
a frame comprising spaced longitudinal members extending between spaced
transverse members;
ventilated support means carried by the frame for providing support, in
instances when a pressure differential exists across the frame, to the
filter core on a low pressure side;
the transverse members including retaining means for releasably retaining
the proximate transverse edges or edge-margins of the loaded filter core;
and,
at least one longitudinal member including a flap pivotally attached
thereto by means of a piano hinge arrangement, the flap extending
longitudinally substantially completely between the spaced transverse
members and being pivotal between closed and open positions for allowing
retention and unobstructed removal in the closed and open positions,
respectively, of the proximate longitudinal margin of the loaded filter
core, for protecting, when closed, the proximate longitudinal margins of
the pleats of the pleated-media of the filter core from damage during
sliding installation of the support rack in slideways for said support
rack in the filter station of the air-handling equipment, and, when open,
for allowing convenient unloading and replacement of the filter core;
wherein said flap while closed further provides a bearing surface for
sliding contact with the slideways of the filter station during sliding
installation; and whereby said flap obviates the need for a lock for the
closed position because while in the slideways, said slideways oppose the
flap's movement out of the closed position.
2. The support rack of claim 1 wherein the flap is one leaf of a piano
hinge.
3. The support rack of claim 1 wherein the other longitudinal member also
includes a flap pivotally attached thereto by means of a piano hinge
arrangement.
4. The support rack of claim 1 wherein the retaining means included with
the transverse members comprises a finger.
5. The support rack of claim 1 wherein the ventilated support means
comprises a web of expanded metal.
6. The support rack of claim 1 wherein the frame members are angle members
fixed together at corners of the frame.
7. A support rack for loading and unloading with replaceable, pleated-media
filter cores that have fold lines extending in a transverse direction and
which stretch-out/collapse in a longitudinal direction, the loaded support
rack allowing installation in a filter station of air-handling equipment,
the support rack comprising:
a frame comprising spaced longitudinal rails extending between spaced
transverse rails;
the transverse rails including retaining means for releasably retaining the
proximate transverse edges or edge-margins of the loaded filter core; and,
at least one longitudinal rail including a flap pivotally attached thereto,
which flap extends longitudinally substantially completely between the
spaced transverse rails, and which can be pivot between use and non-use
positions for allowing retention and unobstructed removal in the use and
non-use positions, respectively, of the proximate longitudinal margin of
the loaded filter core, for protecting, while in the use position, the
proximate longitudinal margins of the pleats of the pleated-media of the
filter core from damage during sliding installation of the support rack in
slideways for said support rack in the filter station of the air-handling
equipment, and, when in the non-use position, for allowing convenient
unloading and replacement of the filter core;
wherein said flap while in the closed position further provides a bearing
surface for sliding contact with the slideways of the filter station
during sliding installation; and whereby said flap obviates the need for a
lock for the closed position because while in the slideways, said
slideways oppose the flap's movement out of the closed position.
8. The support rack of claim 7 wherein the flap comprises one leaf of a
piano hinge.
9. The support rack of claim 7 wherein the other longitudinal rail also
includes a flap pivotally attached thereto.
10. The support rack of claim 7 further including a ventilated support
means carried by the frame for providing support, in instances when a
pressure differential exists across the frame, to the filter core on a low
pressure side.
11. The support rack of claim 10 wherein the ventilated support means
comprises a web of expanded metal.
12. A support rack allowing loading and unloading of replaceable
pleated-media filter cores that have fold lines extending in a transverse
direction and which stretch-out/collapse in the longitudinal direction,
the loaded support rack allowing installation in such a filter station of
air-handling equipment that has transversely-spaced,
longitudinally-extending channel-shaped slideways; said support rack
comprising:
a frame for surrounding peripheral margins of a given pleated-media filter
core when stretched out and loaded;
the frame having spaced transverse portions including retaining means for
releasably retaining transverse edges or margins of the given loaded
pleated-media filter core;
the frame also having spaced longitudinal portions that extend between the
transverse portions; each longitudinal portion includes a flap pivotally
attached thereto which extends longitudinally substantially completely
between the spaced transverse portions, and which can pivot between use
and non-use positions for retaining and allowing unobstructed removal in
the use and non-use positions, respectively, of the corresponding
proximate longitudinal margin of the installed pleated-media filter core,
for protecting, while in the use position, the proximate longitudinal
margin of the pleats of the pleated-media of the filter core from damage
during sliding installation of the support rack in the channel-shaped
slideways of the filter station, and, when in the non-use position, for
allowing convenient unloading and replacement of the filter core;
wherein each flap while in the closed position further provides a bearing
surface for sliding contact with the channel-shaped slideways of the
filter station during sliding installation; and
whereby said flaps obviate the need for locks for each flap's closed
position because while in the slideways, said slideways oppose the
movement of the flaps out of each's closed position.
13. The support rack of claim 12 wherein each flap comprises one leaf of a
piano hinge.
14. The support rack of claim 12 wherein the retaining means included with
the transverse portions comprises a finger.
15. The support rack of claim 12 further including a ventilated support
means carried by the frame for providing support, in instances when a
pressure differential exists across the frame, to the filter core on a low
pressure side.
16. The support rack of claim 12 wherein the spaced transverse and
longitudinal portions comprised spaced transverse and longitudinal rails
arranged and fixed together to define a rectangular shape.
Description
BACKGROUND AND SUMMARY OF THE INVENTION
The invention generally relates to replaceable air filters, and, more
particularly to a re-usable frame support rack for supporting and
retaining an outstretched, replaceable pleated-media filter core. The
frame support rack in accordance with the invention is available in
various standard as well as custom sizes, but generally speaking, it is
more advantageous in relatively large sizes as commonly used by
commercial, industrial, and municipal users, and not so much by
residential users.
Conventional air filters typically comprise a complete package of a filter
core and a rigid frame surrounding and permanently attached to the filter
core. The filter core is typically formed from conventional filter media.
The rigid frame is typically formed from paperboard or the like.
Commercial, industrial, and municipal users typically have defined service
policies for the replacement of spent air filters after the filters have
outlasted their usefulness. These kinds of users typically will keep a
stock of fresh conventional filters on supply in a stock room for
replacement purposes. Service personnel are responsible for replacing
spent filters with fresh filters and then disposing of the spent filters.
With conventional filters, each time a filter is replaced a complete
package is discarded as refuse, comprising the rigid frame and its
attached filter core.
It is an object of the invention to provide a re-usable frame support rack
to combine with a replaceable filter core, such as for example a core
comprising pleated filter media, in order to provide economy in filter
replacement costs, service personnel labor costs, stock room storage space
requirements, refuse volume, and so on.
It is known in the art, however, to provide a fixed frame for supporting a
pleated-media filter core. To assign reference directions to the
pleated-media core, it stretches out in a longitudinal direction, and its
pleats or fold-lines extend in a transverse direction. A prior art fixed
frame is constructed from a single straight channel piece. In fabrication,
the straight channel will be notched at the location of the four corners
of the frame. Then the notched straight-channel piece will be bent into
the rectangle shape of the frame, and welded or brazed tight. The final
frame thus will have opposite longitudinal channel sections facing each
other (as well as opposite transverse channel sections too). The spaced,
facing channel sections act to cup the spaced longitudinal margins of the
outstretched pleated-media filter core.
Given a typical orientation, the opposite longitudinal channel sections
usually define the top and bottom borders of the prior art fixed frame.
The top and bottom channels protect the pleated media of the filter core
from damage during installation of the frame in any given on-site
air-handling system. That is, the fixed frame usually installs in the
on-site air-handling equipment by sliding into opposed tracks or slideways
for it in a filter-station of the on-site air-handling equipment.
Therefore, the top and bottom channels of the frame consequently provide
the following features:--(i) the top and bottom channels act as bearing
surfaces to facilitate sliding in the slideways, and (ii) the top and
bottom channels protect the pleated media of the filter core from damage
such as being grabbed, torn or otherwise pulled at by the slideways of the
on-site air-handling equipment.
There are shortcomings with the prior art fixed frame for pleated-media
filter core. The pleated-media filter core can only be loaded and unloaded
into the rigidly spaced top and bottom channel sections, and then
stretched out between the left and right channels sections, in an awkward
way. To load the filter core, the pleated-media must start out
substantially collapsed, and then it is placed in the interspace between
the top and bottom channels twisted slightly off-angle. The collapsed
media is next twisted perpendicular to the opposed top and bottom channels
such that its opposite edges insert between and are hence cupped by the
opposed top and bottom channels. After that, the pleated-media is
stretched out to the left and right extremes, all while its opposite
longitudinal edges are sliding in the top and bottom channels to unfold to
its fully outstretched use position.
The filter core is unloaded from the prior art frame by the reverse steps.
More particularly, the filter core is collapsed by sliding its
longitudinal edges in the opposed top and bottom channels until
substantially collapsed. The collapsed filter core is then twisted such
that its longitudinal edges twist out of the top and bottom channels. Once
that has been accomplished, the filter core can be lifted out away from
the fixed frame.
In view of the foregoing shortcomings of the prior art, it is an object of
the invention to provide a re-usable frame support rack for replaceable
pleated-media filter core which allows loading and unloading by means of
much less fuss.
A number of additional features and objects will be apparent in connection
with the following discussion of preferred embodiments and examples.
BRIEF DESCRIPTION OF THE DRAWINGS
There are shown in the drawings certain exemplary embodiments of the
invention as presently preferred. It should be understood that the
invention is not limited to the embodiments disclosed as examples, and is
capable of variation within the scope of the appended claims. In the
drawings,
FIG. 1 is a perspective view of an empty, re-usable frame support rack in
accordance with the invention, for supporting a replaceable filter core;
FIG. 2 is a perspective view comparable to FIG. 1, except showing the frame
support rack loaded with a replaceable pleated-media filter core;
FIG. 3 is an enlarged perspective view of, in isolation, a side angle of
the frame support rack (i.e., the left side as the rack is viewed in FIG.
1);
FIG. 4 is a perspective view of pleated filter media, partly outstretched,
formed with a terminal edge on the left, and extending to the right with
portions broken away out of view (i.e., the reference directions left and
right being relative to the vantage point for FIG. 4); and,
FIG. 5 is a sectional view showing the interconnection between the side
angle of FIG. 3 and the terminal edge of the filter media shown by FIG. 4.
DETAILED DESCRIPTION OF THE REFERRED EMBODIMENTS
FIGS. 1 and 2 show a frame support rack 10 in accordance with the
invention, for supporting and retaining a replaceable filter core 12. In
FIG. 2, the support rack 10 is loaded with a pleated-media 14 filter core
12, whereas in FIG. 1 the support rack 10 is unloaded and empty as the
filter core 12 has been removed. The support rack 10 is made from durable
materials such as galvanized steel or the like for an indefinitely long
life, as for re-use over and over with numerous replaceable filter cores
12.
The frame support rack 10 comprises a pair of relatively elongated
longitudinal angles 20 extending between a pair of transverse angles
22-23. These angles 20 and 22-23 of galvanized steel are lapped and
fastened or clinch-locked or otherwise affixed together at the corners to
form an open-box like frame configuration. Presently it is preferred if
the angles 20 and 22-23 are affixed by machine-pressed clinch-lock
formations.
In the drawings, the transverse angles 22-23 are shown relatively left and
right of each other as the support rack 10 is shown resting on a flat
support surface (which is not shown). The support rack 10 can be oriented
and/or mounted, however, in any orientation, and accordingly, terms like
"longitudinal" and "transverse" or "left" and "right" are used merely for
convenience in this description and do not limit the invention to a
particular orientation, regardless if in use or at rest between uses.
However, with reference to FIG. 2, the terms "longitudinal" and
"transverse" are used in this description--again for purposes of
convenience only and not of limitation--to denote the following reference
directions relative to the pleated-media filter core 12. The reference
direction "longitudinal" is used herein to designate the direction
relative to the pleated-media filter core 12 in which it reversibly
stretches-out and/or collapses, accordion style. Correspondingly, the
reference direction "transverse" is used herein to designate the direction
in which the fold- or pleat-lines extend. Hence the pleated-media filter
core 12 is expansible and/or collapsible (e.g., accordion style) in the
longitudinal direction (indicated by reference numeral 16 in the
drawings). In the transverse direction (indicated by reference numeral
18), the pleated-media filter core 12 is relatively rigid. It is
significant that, the pleated-media filter core 12 cannot be practicably
collapsed or foreshortened in the transverse direction 16 without buckling
or damaging it.
The longitudinal and the left and right transverse angles 20 and 22-23
define a rectangular opening between themselves and carry an expanded
metal "support" or reinforcement system 24. The expanded metal support
system 24 provides--when the filter core 12 is loaded into the frame
support rack 10 (as shown by FIG. 2)--support against or oppositions to
the tendency of the filter core 12 to buckle or blow out under air
pressure or flow when the filter core is pressurized on the opposite side
(i.e., the side of the filter core 12 that is in full view in FIG. 2).
The expanded metal support system 24 extends the full span between and
overlaps onto the inward flange portion of each of the longitudinal as
well as the left and right transverse angles 20 and 22-23 (see FIG. 1).
The expanded metal support system 24 is fastened or locked onto these
flange portions via punched or lanced tabs 25. The punched or lanced tabs
25 are originally formed to extend straight out from their bases in the
flange portions (not shown, but refer to FIG. 3 for an illustration of
punched or lanced tab formations 34). Then, after the expanded metal
backing 24 has been inserted over the straight-up tabs 25 (not
illustrated), the tabs 25 are bent over to lock or retain the expanded
metal support system 24 securely to the frame rack 10.
Each longitudinal angle 20 has a piano hinge 26 attached to it. The piano
hinges 26 extend substantially the entire length of the longitudinal angle
20 to which each is attached, and form a hinge flap--or in alternative
phraseology, a gate or a fence--for it. More particularly, the hinge flaps
26 are one leaf of the piano hinge, the other piano-hinge leaf being
secured to the proximate longitudinal angle by clinch lock formations or
the like. The hinge flaps 26 are free to swing between extremes of at
least an open position as generally shown by FIG. 1, and a closed position
as shown by FIG. 2. The whole assembly 10 of angles 20,22-23 and piano
hinges 26 are preferably protected against rust or moisture attack with an
enamel or a like polymeric--or resinous-material coating.
The support rack 10 defines a box-like frame for supporting and retaining
the outstretched filter core 12 as is shown in FIG. 2. The support rack 10
can be produced in any standard and/or custom size. The size for the
support rack 10 is presumably predetermined by the air-filtration
installation and/or equipment (not shown) which the support rack 10 will
service. The filter core 12 size is determined accordingly.
There are certain standard sizes in the industry of air filtration.
Standard ranges for the dimension between the longitudinal angles 20
include, without limitation, sixteen, twenty, twenty-four and twenty five
inches (forty, fifty, sixty, and sixty-four cm, respectively). The length
between the transverse angles 22 and 23 can be about anything, custom or
standard, say, for sake of example, about five feet (one and one-half
meters) or so. The depth between front and back typically is sized for
filter cores that require a two-inch (five cm) depth, although one--as
well as four-inch (two and one-half and ten cm) depths are also known.
Closing the hinge flaps 26 as shown in FIG. 2 assists in containing the
outstretched filter core 12 in the rack 10. The hinge flaps 26 also
provide, among other matters, protection to the proximate longitudinal
margins of the pleated media of the filter core 12. The rack 10 and filter
core 12 combination are shown ready for installation. In use, the rack 10
is typically installed or mounted by orienting it vertically and sliding
it, drawer-like, between opposed tracks or slideways (not shown) for it in
at a given filter-station of the on-site air-handling equipment(not
shown). Such tracks or slideways are typically sections of channel (not
shown). The channel-shaped tracks or slideways (again, not shown) for
mounting the rack 10 assist in holding the hinge flaps 26 in their closed
positions as shown by FIG. 2. The rack 10 and filter core 12 is preferably
oriented relative to the direction of air flow such that hinge flaps 26
are on the upstream or high-pressure side of the filter-station (i.e.,
which corresponds to a down flow on the rack 10 as it is oriented in FIG.
2).
In use, after the filter media 14 is spent, the filter core 12 ought to be
replaced. FIG. 1 shows that the hinge flaps 26 swing open (i.e., or "up"
in FIG. 1) and out of the way to allow convenient, unobstructed removal of
the spent filter core 12 by lifting it directly out, and without having to
collapse the filter core between its left and right edges (left edge or
margin indicated as reference numeral 32 in FIG. 4 or 5). Accordingly, the
frame support rack 10 is re-usable while the pleated-media 14 filter core
12 is replaceable. In use, this combination of an indefinitely re-usable
frame 10 with a replaceable filter core 12 provides numerous advantages,
including without limitation the following.
It is economical that the frame 10 is re-usable. Only the filter core 12 is
replaced and discarded. In other words, the replacement cost is limited to
the cost of the filter core 12, it does not include the reusable frame 10.
This situation represents around a 50% savings relative to a conventional
package of a rigid paperboard-frame and attached core (not shown). With
conventional paperboard-frame filters (again, not shown), the entire
package of a filter core and attached frame is disposed of after service.
Another economy provided by the invention is an economy of storage space.
There is no practical need to provide storage space for the frame 10
because it is kept at its installation site as if it were accessory
equipment for the on-site air-handling equipment (not shown) in which the
rack 10 is installed. Only storage space for the replaceable filter cores
12 needs to be provided. The filter cores 12, being formed from a pleated
filter media 14, are highly collapsible, accordion-style, to a fraction of
their volume when outstretched. A highly collapsed replacement core 12 in
accordance with the invention provides about a 90% savings in storage
space relative to its conventional counterpart (i.e., the rigid
paperboard-frame and attached filter core combination, not shown).
A spent filter core as one like indicated by reference numeral 12, is also
90% less bulky in a refuse bin and/or land fill space relative to its
conventional counterpart, because the spent filter core 12 is as just as
highly collapsible when spent as when new.
In a situation where one can do the work of three, a lone frame 10 in
accordance with the invention allows adaptation for use in situations
where the job would ordinarily be handled by three conventional
paperboard-frame/filter packs. For example, a filter installation or
station having a dimension or cross-section of about five feet by two feet
(one and one-half meters by sixty cm) might be serviced by three
conventional paperboard-frame/filter packs that measure twenty-four by
twenty inches (sixty by fifty cm), as aligned side by side to extend
across the whole cross-section. Despite that three side-by-side
conventional filter packs would leave gaps between one another, users
typically tolerate the gaps for the convenience of stocking and handling
three times as many less bulky packs than one measuring the complete five
feet by two feet (one and one-half meters by sixty cm). The invention
solves the foregoing problem because the only actual bulky component is
the frame support rack 10. However, the frame support rack 10 is more or
less permanently kept at the installation site and need not travel through
the stock room after original installation. Servicing requires--not
keeping a supply of bulky frames 10 on hand, but--merely keeping on hand a
supply of the highly compact pleated-media filter cores 12.
The invention also provides economy in the cost of labor for servicing
spent filter cores 12. The filter cores 12 are packaged for stock room
storage in compact packages because the cores are compressed into a highly
collapsed state for packaging purposes. This allows service personnel to
handle perhaps ten times as many of the highly-collapsed filter cores
packages (not shown) relative to conventional paperboard-frame/filter
packs, which are perhaps ten times as more bulky. Service personnel are
likely to spend fewer out and back trips traveling between filter
installations and stock rooms.
The filter media 14 is pleated, which not only gives the filter core 12
extra surface rigidity, but also gives the filter core 12 a longer
use-life relative to flat media because the pleated media 14 presents more
surface area relative to flat media, perhaps effectively twice as much.
FIGS. 3 through 5 show how one of the opposite transverse edges or
edge-margins 32 of a pleated-media 14 filter core 12 (i.e., the left
transverse edge and margin is shown, as representative of the opposite
right transverse edge and margin, which is not shown) attaches to the
corresponding transverse angle 22/22' of the support rack 10. As the
invention is shown in FIG. 3, the transverse angle 22/22' can be either
(i) formed with sets of punched or lanced tabs as indicated by reference
numeral 34, or alternatively, (ii) formed with affixed L-shaped pads as
indicated by reference numeral 34'. However, the disclosure of either
L-shaped pads 34' or punched or lanced tabs 34 are both shown as
non-limiting examples of how to form transverse angle 22/22' with
projections or "fingers" to hook or grip the transverse edge or margins 32
of the pleated-media filter core 12. Accordingly, the depiction and
description of L-shaped pads 34' and/or punched or lanced sheet metal tabs
34 are used merely for convenience in this description and do not limit
the invention to a particular means of retention of the transverse edges.
It is conventional, although, to avoid welded bonds with galvanized metal
parts because the welding process deteriorates the anti-corrosive
protection otherwise provided by galvanized metal. Hence it is preferred
if the L-shaped pads 34' are used, and further that the L-shaped pads 34'
be attached by means of machine-pressed clinch-lock formations, as
mentioned above.
FIG. 4 shows that the filter core 12 has a paperboard strip 36 attached
along its transverse edge or margin 32. FIG. 5 shows that the tabs 34 or
34' of the transverse angle 22 or 22' retain the transverse edge (or
margin) 32 of the filter core 12 by extending between the paperboard strip
36 and filter media 14. With reference back to FIG. 2, the act of swinging
the hinge flaps 26 closed assists in holding the opposite transverse edges
32 of the filter core 12 in position as shown therein.
As previously mentioned, the support rack 10 is typically installed or
mounted in the on-site air-handling equipment by sliding it between
opposed channel-shaped tracks or slideways for it at a given filter
station (this is not shown). The hinge flaps or fences 26 are useful in
acting as bearing surfaces for sliding contact with the channel-shaped
slideways. Without the flaps or fences 26, the channel-shaped slideways
would damage the pleats of the filter core 12 (this also is not shown) by
means of grabbing, pinching, tearing, or otherwise pulling at them. Hence
it is sufficient that the flaps or fences 26 merely move into their use-or
closed-positions as shown by FIG. 2 to provided protection to the pleats
against the channel-shaped slideways. The flaps or fences 26 also
facilitate sliding contact and hence function as bearing surfaces. It is
not necessary that the flaps or fences 26 lock in their use-or closed
positions. The channel-shaped slideways (not shown) oppose the flaps or
fences 26 from moving out of their use- or closed-positions during the
following times or events:--that is, (i) during the time that the frame 10
is installed, (ii) during installation of the frame 10, and (iii) while
the frame 10 is being slid out of installation for servicing.
The invention having been disclosed in connection with the foregoing
variations and examples, additional variations will now be apparent to
persons skilled in the art. The invention is not intended to be limited to
the variations specifically mentioned, and accordingly reference should be
made to the appended claims rather than the foregoing discussion of
preferred examples, to assess the scope of the invention in which
exclusive rights are claimed.
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